OS L3

What is the main advantage of virtual memory?

• Reduces processor overhead
• Allows program execution even if not stored entirely in memory
• Eliminates page faults
• Increases secondary storage speed

Which of the following are memory allocation methods? (Select all that apply)

• Paged memory allocation
• Demand paging
• Segmented memory allocation
• Contiguous memory allocation

In a paged memory system, what is the best condition for page size?

• Page size should be larger than memory block size
• Page size should be smaller than disk sector size
• Page size should be equal to memory block size and disk sector size
• Page size does not affect system performance

Which of the following is a disadvantage of paged memory allocation?

• Reduces fragmentation
• Eliminates the need for a memory map table
• Increases overhead due to address resolution
• Allows only contiguous memory allocation

What does a Page Map Table (PMT) store?

• Page number and corresponding page frame address
• The entire job’s instructions
• Status of CPU registers
• The execution order of processes

In demand paging, when is a page loaded into memory?

• Before the program starts execution
• Only when it is required for execution
• During program compilation
• After the program terminates

What occurs when a requested page is not in memory?

• CPU fetches the page from cache
• A page fault occurs
• The program is terminated
• The memory manager ignores the request

What is thrashing in virtual memory?

• The process of relocating pages in memory
• Excessive page swapping between main memory and secondary storage
• When all pages are present in memory
• A technique used to speed up execution

Which of these are page replacement policies? (Select all that apply)

• First-In First-Out (FIFO)
• Least Recently Used (LRU)
• Most Frequently Used (MFU)
• Clock replacement

What is the main problem with FIFO page replacement?

• It always selects the most frequently used page
• It can replace pages that are still actively needed (Belady’s anomaly)
• It reduces the number of page faults
• It requires extra CPU registers